JPS61261979A - Compensating system for drop-out of video signal - Google Patents

Abstract

PURPOSE:To perform a good drop-out compensation by interrupting an input to a noise reducing device and outputting a signal of two frames before from the noise reducing device when a drop-out is occurred at a reproducing device. CONSTITUTION:The reproducing output signal an MUSE system from a reproduc ing device 14 is supplied to a noise reducing device 3 through an A/D converter 2 and supplied to frame memories 4 and 5. And the signal through a still picture filter 6, a moving picture picture filter 7 and a motion detecting circuit 8 is sent to a mixer 9 and becomes a video signal. When the drop-out is detected at the reproducing device 14, a data selector 34 in the noise reducing device 3 is made to be earth potential and a coefficient K at a coefficient circuit 32 is compulsorily set to K=-1. Therefore, the signal of two frames before is outputted as the input to the memory 4. Thus, a good drop-out compensation can be obtained.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Outline of the invention C. Prior art (Figs. 3 to 5) D. Problem to be solved by the invention E. Means for solving the problem (Fig. 1) F. Effect G. Implementation Examples (Figs. 1 and 2) Effects of the Invention A Industrial Application Field The present invention provides a video signal drop arrangement suitable for use in a sub-Nyquist sampled and dot interleafed signal reproducing device. −? ii Compensation Method B Summary of the Invention The present invention comprises a reproduction device for a video signal subjected to sub-Nyquist sampling and dot interleafing, and a noise reduction device that performs noise removal using a reproduction signal two frames before. When a dropout occurs in the signal, the reproduced signal two frames before is extracted from the noise reduction device to perform dropout compensation.

C Conventional technology A new transmission method for so-called high-definition television is M [IS
I! (Multiple 5ub-Nyquist
Sampling Encoding) method has been proposed (Preliminary of the Foundation Commemoration Lecture, "New Transmission Method for High-Definition Television (MUSE)" J, Tasuku Ninomiya-1 June 6, 1980, NHK Research Institute of Broadcasting Science. Institute).

In other words, in this method, if there is a luminance signal Y and a color difference signal cN-cw as shown in FIG. The time axis is compressed and inserted into the horizontal blanking period at the leading end of each corresponding luminance signal Y in line order to form a TCI signal as shown in the figure. This TCI is sampled at 64.8MIIz as shown in Figure E, and one sample is extracted from every 4 samples of this sampling data, and dot interleafed with each other as shown in Figure F. A sub-Nyquist sampling signal is formed that goes around the field. Therefore, the frequency of sub-Nyquist sampling becomes 16.2 MHz, and thereby the baseband signal bandwidth, which was originally 20 M11z, can be compressed to 8.1 M11z. This signal is transmitted via, for example, a frequency modulation (FM) L/broadcasting satellite.

On the receiving side, on the other hand, the received signal is demodulated and the above-mentioned 8.1 MI
A sub-Nyquist sampling signal of Iz is extracted. Sample this signal at 16.2 MHz, write this sampling data to the memory as shown in E in the above figure, and then write these data and the data at the non-sampling points indicated by blanks in G in the same figure. The conversion and interpolation are performed to restore the TCI signal as shown in D in the above diagram. From this signal, a luminance signal Y and a color difference signal Cw-Cw as shown in A-C in the above-mentioned figure can be extracted.

How to get high definition TV signal? The IUSE system enables transmission through one channel of satellite broadcasting with a bandwidth of, for example, 27 MHz.

On the above-mentioned receiving side, signal restoration was specifically performed as follows.

In FIG. 4, the above-mentioned received and demodulated HUSB system signal is supplied to the input terminal (1). This signal is AD
A predetermined clock signal is also supplied to the AD conversion circuit (2), where it is sampled using this clock signal and digitally converted into, for example, 8 bits.

This digital signal is supplied to serially connected frame memories (4) and (5) through a noise reduction device (3).

The input signal and output signal of this memo (January 4) are supplied to a filter (6) for restoring a still image, and the input signal of the memory (4) is supplied to a filter (7) for restoring a moving image. Further memo January 4) human output (fs issue and memo January 51)
The output signal of the filter (6) (?) is supplied to the motion detection direction II (8), and the detection output controls the mixing circuit (9) to which the output of the filter (6) (?) is supplied. This signal is supplied to the field interpolation circuit (10), and the interpolated luminance signal Y
is directly supplied, and the color signal C is supplied to a DA conversion circuit (12) through a TCI decoder (11), and the restored luminance signal Y and color difference signals CM and Cυ are taken out to an output terminal (13).

As a result, the transmission signal of the MtISE method is subjected to predetermined filtering in the still image area and the moving image area, and then subjected to field interpolation and TCI decoding to restore and output a high-quality video signal.

Furthermore, in the device described above, the output signal of the frame memory (5) is fed to the noise reduction device (3). Here, in the noise reduction device (3), the output signal of the memory (5) is subtracted by the subtracter (31) from the output signal of the AD conversion circuit Ia (21), and this subtracted signal is multiplied by the coefficient circuit (32). 0<
K<1) and is added to the output signal of the AD conversion circuit (2) by an adder (33). Therefore, this noise reduction device (3
)'s -10,000 input signal (output signal of AD conversion circuit (2))
The signal component is St), and the noise component is N.

If the signal component of the other input signal (output signal of memory (5)) is 82 and the noise component is N2, then device (3)
The output signal 5out of is 5out = So +N.

+K (So +NO(S2 +N2)),
Here, in the case of a still image, So'-32 becomes 5out = So + (No +K (N
o N21).

By the way, it is being considered to record the above-mentioned FIIJSE signal using a video tape recorder or the like. In that case, it is necessary to take measures to compensate for so-called dropouts. Dropout compensation for a conventional playback device (14) such as a video tape recorder has been performed as shown in FIG.

In the figure, the signal from the playback head etc. is input to the input terminal (41).
This human input signal is taken out to an output terminal (44) through a reproducing circuit (42) and a switch (43).

This output signal is also supplied to the switch (43) through the 1-line memory (45), and the signal from input terminal +11 is further supplied to the dropout detection circuit (46), and when a dropout occurs at this detection output, The switch (43) is switched to the memory (45) side.

As a result, when a dropout occurs, it can be compensated for using the signal from one line before.

However, in the case of the above-mentioned MlJSE system signal, since the color signal is transmitted line-sequentially, it is not possible to obtain the necessary color signal even if compensation is performed using the IPO signal before the line (1). Furthermore, as shown in F in the explanatory diagram of the MUSIi method, the signal one line before was subjected to dot interleafing, so even with this, the necessary signal could not be obtained.

Therefore, it has been proposed to use a signal from two frames (four fields) before the motion detection circuit (8) to compensate with a signal at the same position, but it is necessary to route an 8-bit signal line just for this purpose. However, it is not desirable to provide a data selector for switching, considering that dropout compensation is originally an additional element.

D. Problems to be Solved by the Invention Conventional dropout compensation has been performed in the manner described above. This has led to problems such as a complicated configuration and poor compensation.

E. Means for Solving the Problems The present invention has a dropout detection means (circuit (45)), and sequentially transmits four-field units whose bands are compressed by sub-Nyquist sampling and mutually dot-interleafed. A playback device (
14), and a noise reduction device (3) configured to obtain a playback output with less noise by mixing the playback output of the playback device with the playback output of two frames before (Frame Memo January 5)), This video signal dropout compensation system is such that when a dropout is detected in the playback device, the noise reduction device outputs the signal from two frames before.

F Effect According to this method, the human power of the noise reduction device is cut off by the dropout detection signal, and the coefficient is forcibly set to -1, so that the signal from two frames before is output as the output of the noise reduction device. Therefore, good dropout compensation can be achieved with almost no extra configuration.

G Embodiment In FIG. 1, a reproduction output signal from a reproduction device (14) is supplied to an AD conversion circuit (2), and a digitally converted signal is supplied to a noise reduction device (3).

In this reduction device (3), the signal from the AD conversion circuit (2) is selected as the ground potential by the data selector (34), and this selected signal is sent to the subtracter (31) and adder (33).
is supplied to Furthermore, a signal from the dropout detection circuit (45) of the playback device (14) is supplied, and when a dropout is detected, the ground potential is selected by the data selector (34), and the coefficient of the coefficient circuit (32) is K is forced to =-1.

Therefore, when dropout is detected in this device, the output signal 5out of device (3) becomes 5out −
32+N2, and when there is an input signal like A and a dropout detection signal like B in the time chart of Figure 2, the output signal of Memo January 5) is delayed by 2 frames (4 fields) and becomes D. It looks like this, and the memory (4)
As shown in C, a dropout-compensated signal from two frames earlier is supplied to the human input.

This is how dropout compensation is performed,
According to the above-mentioned method, since signals are switched using the noise reduction device (3), there is no need to newly provide an 8-bit signal line, etc., and the data selector (34)
Since one of the options is ground, a simpler configuration can be used compared to the one for data exchangers. Further, this data selector may be configured to mute the output of the AD conversion circuit (2).

Therefore, dropout compensation can be performed with an extremely simple configuration, and since this dropout compensation is performed using a signal two frames before, extremely good compensation can be performed. Note that on the playback device (24) side, the conventional one-line memory etc. can be omitted by simply providing the detection circuit (45).

H Effects of the Invention According to the present invention, by blocking the input of the noise reduction device using the dropout detection signal and forcibly setting the coefficient to -1, the signal of two frames before is output as the output of the reduction device. As a result, it is now possible to perform good dropout compensation with almost no extra configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of the present invention, FIG. 2 is a diagram for explaining the same, and FIGS. 3 to 5 are diagrams for explaining a conventional device. (3) is a noise reduction device, (41 (5) is a frame memory, (14) is a playback device, and (45) is a dropout detection circuit.

Claims (1)

[Claims] A playback device that has a dropout detection means and plays back a video signal in which four-field screens that are band-compressed by sub-Nyquist sampling and dot interleafed with each other are sequentially transmitted; and a noise reduction device configured to obtain a playback output with less noise by mixing the playback output with the playback output, and when a dropout is detected in the playback device, the noise reduction device outputs the signal from the previous two frames. A dropout compensation method for video signals that can be obtained as follows.